Tooth formation of internal gears



s. HDLDENER TOOTH FORMATION OF INTERNAL GEARS Original Filed March 13,1924 jhveniol? are Patented May 19, 1925. Y

UNITED STATES SIMON HOLDENER, OF WOLFSHAUSEN, SWITZERLAND.

TOQTH FORMATION OF INTERNAL GEARS.

Original application filed March 18, 1924, Serial No. 698,984. Dividedand this application filed December 15, 1924. Serial No. 756-,023.

To all whom it may concern Be it known that I, SIMON Hononunn, a citizenof the Republic of Switzerland, residing at Wolfshausen, Switzerland,have invented certain new and useful Improvements in Tooth Formation ofInternal Gears, of which the-following is a speci fication, referencebeing had therein to the accompanying drawings.

The present application, which is a divisional application of myapplication Ser. No- 698,984, filed March 13, 1924, relates toimprovements in the tooth formation of internal gears, which gears areparticularly applicable to transmission gears such as disclosed in theabove mentioned earlier application.

With the present tooth. formation the flanks ot' the teeth of the outerand the inner toothed rims comprising circular arcs of the same radius,which corresponds to the radius of the smaller pitch circle and thecentre of said arcs of the teeth of the inner rim bein situated on thepitch circle of the latter ant the centre of the arcs of the teeth ofthe outer rim being situated on an auxiliary circle which is concentricto the pitch circle of the outer rim, the auxiliary circle passingthrough the centres of curvature of the flanks of a tooth of the smallerwheel when the latter is in its extreme position of engagement so thatcontact surfaces between cooperating teeth are obtained that are aslarge as possible.

This effect in combination with a favourable cross-sect ion of the teethensures that with the gear running in an oil-bath between cooperatingteeth a comparatively large oilpressure surface is obtained and anoiseless running of the gear.

A constructional example of an internal gear showing the tooth formationaccording to the present invention is illustrated on the accompanyingdrawing in an elevation view, with parts illustrated in section.

In the drawing two co-operatiug toothed rims 8 and 9, which areeccentric to each other, are illustrated. The toothed rim 8 isinternally toothed, the number of teeth being 34, and the toothed rim 9is provided with 30 external teeth. M denotes the centre of the toothedrim 9 which is provided, for instance. on the transmitting member 9carrying out eccentric movements as disclosed in the specification Ser.No. 698,98i. T and T are the pitch circles of the toothed rims S and 9,the pitch circles contacting in N, the toothings have diametral pitch. Astraight line passing through M and N forms the centre line of the toothO of the rim 9 which is the position of its maximum engagement. P and Pare the points of intersection of the faces of the tooth 0 with thepitch circle T. Q, designates an auxiliary circle having the centre M,the diameter of this circle being equal to the radius of the smallerpitch circle T.

In order to obtain the centres of the circular arcs forming the flanksof the tooth O arcs R and B respectively are drawn from the points P. 1respectively as centres and with a radius that is equal to the radius ofthe pitch circle T, the arcs intersecting this pitch circle in S and SThe points of intersection S and 8 obtained in this manner repre ent thecentres of the circular arcs U and U respectively, forming the flanks 0tthe tooth O. The straight lines V and V respectively passing through thepoints S,

vP and S P respectively are perpendicular on the tangents \V andrespectively passing through the points P and P respectively andcontacting with the auxiliary circle Q. The shape of the tooth O scompleted by drawing the addendum circle and the dedendum circle.

To this shape of tooth the shape of the co-operating tooth X of the rim8 corresponds. The flanks of thetooth X- are formed by circular arcshaving the same radius as the flanks of the tooth O. The centres ofcurvature of the flanks of the tooth X are situated on the auxiliarycircle T which is concentric to the pitch circle T of the toothed rim 8and passes through the points of intersection S and S The smallclearance of the co-operating flanks required owing to the smalldifference in the number of teeth of the two rims is provided by theelasticity of the material together with the small limits used in manufacturing the teeth.

In order to obtain the necessary clearance at the bottom of the teeththe root of tooth is chosen larger than the point of tooth in the mannerknown withtoothings having diametral pitch. The distance between theaddendum circle and the dcdendum circleand the pitch circle may also bechosen in a diil'erent manner to that illustrated.

The co-operating teeth possess a favourable cross-section and largecontacting surfaces so that between these surfaces large oil pressuresurfaces are formed when the gear works in an oil-bath, whereby anoiseless working of the gear is attained.

To ensure a better working of the two toothed rims with a greaterdifl'erence in the number of teeth the flanks of the teeth of theinternally toothed rim 8 on the point of the teeth may advantageously beformed as flat surfaces. The flanks above thepitch circle are preferablyshaped according to the tangents \/V and WW respectively, which aredrawn to contact with the auxiliary circle Q concentric to the pitchvcircle of the outer toothing from the point of intersection between theflank of the space of tooth at the point of maximum engagement and thepitch circle.

I claim:

1. In an internal gearing two eccentric toothed rims, the flanks of theteeth of the outer and of the inner toothed rims comprising circulararcs of the same radius, which corresponds to the radius of the pitchcircle of the inner rim, the centre of said arcs of the teeth of theinner rim being situated on its pitch circle and the centre of said arcsof the teeth of the outer rim being situated on an auxiliary circlewhich fianks of the teeth is concentric to the pitch circle and whichpasses through the centres of curvature of the flanks of that tooth ofthe smaller rim which is in maximum engagement.

2. In an internal gearing two eccentric toothed rims, the flanks of theteeth of the outer and of the inner toothed rims comprising circulararcs of the same radius, which corresponds to the radius of the pitchcircle of the inner rim, the centre of said arcs of the teeth of theinner rim being situated on its pitch circle and the centre of said arcsof the teeth of the outer rim being situated on an auxiliary circlewhichis concentric to the pitch circle and which passes through thecentres of curvature of the flanks of that tooth of the smaller rimwhich is in maxi-,

mum engagement, and the portion of the of the outer rim on the addendumof tooth being defined by straight llnes corresponding to a tangentdrawn from the point of intersection of the flank of the space oftoothin the point of maximum engagement with the pitch circle to anauxiliary circle which is concentric to the pitch circle of the innerrim and the diameter of whiph is equal to the radius of said pitch circe.

In testimony whereof I aflix my signature.

SIMON HOLDENER.

